1. Field of the Invention
The present invention relates generally to techniques for performing wellsite operations. More specifically, the present invention relates to techniques, such as blowout preventers (BOPs) and/or ram blocks, for sealing wellbores.
2. Background of the Related Art
Oilfield operations are typically performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites, and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Once the downhole tools form a wellbore to reach a desired reservoir, casings may be cemented into place within the wellbore, and the wellbore completed to initiate production of fluids from the reservoir. Tubing or pipes are typically positioned in the wellbore to enable the passage of subsurface fluids to the surface.
Leakage of subsurface fluids may pose a significant environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), are often positioned about the wellbore to form a seal about pipes therein to prevent leakage of fluid as it is brought to the surface. In some cases, the BOPs employ rams and/or ram blocks that seal the wellbore. Some examples of ram BOPs and/or ram blocks are provided in U.S. Pat. Nos. 4,647,002, 6,173,770, 5,025,708, 7,051,989, 5,575,452, 6,374,925, 2008/0265188, 5,735,502, 5,897,094, 7,234,530 and 2009/0056132.
Despite the development of techniques involving ram BOPs and/or ram blocks, there remains a need to provide advanced techniques for preventing leakage of subsurface fluids from wellbores. It may be desirable to provide techniques that provide more effective sealing and/or failure resistance. It may be further desirable to provide techniques that provide positive locking of seals. Preferably, such techniques involve one or more of the following, among others: adaptability to wellsite equipment (e.g., various pipe diameters), enhanced sealing, performance under deflection and/or wellsite equipment failures, distribution and/or absorption of loads, enhanced manufacturing capabilities (e.g., wider tolerances), balanced pressures, and increased capacity (e.g., load, pressure, etc.) The present invention is directed to fulfilling these needs in the art.